Development and analysis of ultrasonic assisted friction stir welding process

Friction stir welding (FSW) has been successfully used for joining low melting temperature materials. However, applications in high strength alloys, such as titanium and stainless steel, remain limited due to large welding force and consequent tool wear. Ultrasonic-assisted processes have been coupled with tooling in various manufacturing processes in order to enhance the performance of conventional machining and bonding processes. We suggest ultrasonic assisted friction stir welding (UaFSW), as a hybrid system, in order to improve the weld quality and welding efficiency of high melting temperature materials.;For successful and effective implementation of the UaFSW process, integration of the ultrasonics on the FSW equipment is necessary, while minimizing vibratory effects on the remaining machine assembly. The UaFSW system is being developed and its mechanism needs to be understood using both the experiments and the numerical simulations. FE simulations of the UaFSW using ABAQUS are carried out to examine plunge forces and temperature profiles during the plunge stage of the process. To gain the fundamental understanding and insights of the process, force and temperature measurement, mechanical testing, and defect analysis are used in studying the influence of the ultrasonic oscillations on the conventional FSW system.;Taking advantage of the characteristics of ultrasonic vibration, the UaFSW of aluminum alloy enables us to decrease the welding force and enhance mechanical properties of welded part in terms of elongation and yield strength. It was shown that ultrasonic integration on FSW tool helps to decrease the chance of formation of welding defect. It could be also observed from the experimental results that ultrasonic vibration helps to decrease the welding forces for welding of high melting temperature material. Force reduction of 6% during the peak region and 12.5% during the welding one was observed. For FE analysis of UaFSW, it was predicted that the plunge forces were reduced by using the ultrasonic vibrations. In addition, it was shown that the plunge forces could be decreased by increasing the amplitude of vibrations.